1. Field of the Invention
The present invention relates to a liquid discharge head that discharges ink and other liquid with the creation of bubbles by utilizing thermal energy. The invention also relates to a head cartridge provided with such head, a liquid discharge apparatus, and a method for discharging liquid.
The present invention is applicable to a printer that records on papers, threads, textiles, cloths, leathers, metals, plastics, glass, woods, ceramics, and other recording media, a copying machine, a facsimile equipment provided with communication system, a word processor or some other apparatuses provided with the printing unit therefor. The invention is also applicable to an industrial printing system complexly structured in combination with various processing apparatuses. Here, in the specification of the present invention, the term xe2x80x9crecordxe2x80x9d means not only the provision of characters, graphics, and other meaningful images, but also, it means the provision of patterns or other images which do not present any particular meaning when recorded on a recording medium.
2. Related Background Art
There has been known the ink jet recording method, that is, the so-called bubble jet recording method, in which energy such as heat is given to ink to cause the change of states thereof accompanied by the abrupt voluminous changes (creation of bubbles), and then, ink is discharged from the discharge ports by the acting force based on this change of states. The ink thus discharged adheres to a recording medium for the formation of images. The recording apparatus using this bubble jet recording method is generally provided with the discharge ports for discharging ink; the ink flow paths communicated with the discharge ports; and the electrothermal transducing devices each arranged in each of the ink flow paths to serve as means for generating energy used for discharging ink as disclosed in the specifications of U.S. Pat. No. 4,723,129, and others.
In accordance with a recording method of the kind, it is possible to record high quality images at higher speeds in a lesser amount of noises. At the same time, for the head that executes this recording method, it is possible to arrange the discharge ports for discharging ink in higher density, among many other advantages, thus obtaining recorded images in higher resolution with a smaller apparatus, as well as obtaining images in colors easily. In recent years, therefore, the bubble jet recording method is widely utilized for many kinds of office equipment, such as printer, copying machine, facsimile equipment, and further, utilized for the textile printing system and others for the industrial use.
Now, along with the wider utilization of the bubble jet technologies and techniques for the products currently in use in many fields, there have been various demands increasingly more in recent years. For that matter, studies and developments have been made in order to satisfy those demands. For example, there has been proposed a method for discharging liquid which is capable of discharging ink in good condition on the basis of the stabilized bubble creation, or, form the viewpoint of higher recording, there has been proposed the improved flow path structure so as to obtain the liquid discharge head which is able to perform the higher refilling into the liquid flow paths.
As an example of such improvement, the flow path structure shown in FIGS. 27A and 27B is disclosed in the specification of Japanese Patent Application Laid-Open No. 63-199972. In this specification, an invention is disclosed in which attention is given to the back waves (the pressure directed in the direction opposite to the one toward the discharge ports, that is, the pressure directed toward the liquid chamber 54). The back waves are not the energy which are directed toward the discharge ports, and function as lost energy.
FIG. 27B shows the valve 55 positioned on the side opposite to the discharge port 18 with respect to the heat generating member 2, which is away from the bubble generating area where bubbles are created by the heat generating member 2 provided for the elemental substrate 1. In FIG. 27B, the valve 55 has its initial position as if it is adhesively bonded to the ceiling of the liquid flow path 10 by the method of manufacture that utilizes flat material or the like, and then, along with the development of a bubble, it is allowed to hang down in the liquid flow path 10. A part of the back waves is controlled by the valve 55 to suppress the energy loss.
However, it is understandable that the suppression of a part of the back waves by the valve 55 thus structured is not necessarily practical for the execution of liquid discharges. The back waves themselves are not directly related to discharges fundamentally as described earlier. At the time when the back waves are generated in the liquid flow path 10, the pressure of the bubble, which is directly related to the discharge, has already in the state that it can discharge liquid from the liquid flow path 10 as shown in FIG. 27B. Therefore, even if a part of the back waves is controlled, there is no significant influence that may be exerted on discharges.
On the other hand, heating is repeated while the heat generating member is in contact with ink for the bubble jet recording method. As a result, deposition is generated due burnt ink on the surface of the heat generating member. Depending on the kind of ink, a deposition of the kind may take place in a considerable quantity so as to make the creation of bubble unstable, and in some cases, it is made difficult to perform ink discharges in good condition. Also, it has been desired to provide a method for executing good discharges without changing the quality of liquid to be discharged even in a case where the quality of liquid used for discharge is easily deteriorated by the application of heat or in a case where it is not easy to obtain sufficient bubbling with the liquid used therefor.
From these points of view, there have been disclosed in the specifications of Japanese Patent Application Laid-Open No. 61-69467, Japanese Patent Application Laid-Open No. 55-81172, and the U.S. Pat. No. 4,480,259 the method uses the liquid (bubbling liquid) for creating bubbles by the application of heat, and the liquid (discharge liquid) which is used for discharging liquid separately so as to transfer the pressure exerted by use of the bubbling liquid to the discharge liquid for discharging that the discharge liquid. In accordance with the discloser in each of them, the discharge ink and the bubbling ink are completely separate by use of silicon rubber or some other flexible film so that the discharge liquid is not directly in contact with the heat generating members, and at the same time, the structure is arranged to transfer the pressure exerted by the bubbling liquid to the discharge liquid by the deformation of the flexible film. With the structure thus formed, it has been attained to prevent the deposition from being accumulated on the surface of the heat generating members, while enhancing the freedom of discharge liquid selection or the like.
However, with the head thus structured to completely separate the discharge liquid and the bubbling liquid, the bubbling pressure is transferred to the discharge liquid by means of the stretching deformation of the flexible film at the time of bubbling. The flexible film absorbs the bubbling pressure to a considerable extent. Also, since the amount of the displacement of the flexible film is not very large, there is a fear that the energy efficiency and the discharge power are lowered, although it becomes possible to obtain the separation effect of the discharge liquid and bubbling liquid.
Therefore, there has been proposed the liquid discharge method and liquid discharge head in which the separation wall is arranged with the provision of each movable members that faces each of the bubble generating areas, and then, the first liquid flow path for use of the discharge liquid and the second flow path for use of bubbling liquid are separated so that the free end of the movable member is displaced by the bubbling pressure to discharge liquid. With the head thus structured, it becomes possible to enhance the energy efficiency and the discharge power, and at the same time, to use the ink which is subjected to being burnt or property changes when heating is applied. Nevertheless, the following problems may be encountered in some cases when a head of the kind is used:
(1) Depending on the robustness or the shape of the movable member, the discharge liquid is allowed to be mixed on the heat generating member (into the second liquid flow path side) due to the negative pressure of the bubble when it is defamed. As a result, the burnt condition occurs or the quality of ink is changed on the heat generating member in some cases.
(2) Also, if the pressure difference takes place between the discharge liquid and the bubbling liquid or if the head is left intact for a long time, the mixture of the discharge liquid and the bubbling liquid may sometimes take place at the aperture between the first liquid flow path and the second liquid flow path.
As described above, if the burnt condition should occur on the heat generating member, the quality of ink should change, or the liquids should be mixed, the life of the heat generating member becomes shorter, and the property of ink changes. These are all the factors that may lead to the problems that the reliability of the head is lowered.
It is one of the objects of the present invention to provide a highly reliable liquid discharge head having excellent discharge efficiency, at the same time, being capable of maintaining separably the characteristics of discharge liquid and bubbling liquid, and also, to provide a head cartridge provided with such head, a liquid discharge apparatus, as well as a method for discharging liquid.
It is another object of the invention to provide a liquid discharge head capable of preventing discharge liquid from entering around the heat generating members at the time of bubble disappearance, and also, preventing discharge liquid and bubbling liquid from being mixed when the head is left intact for a long time, and also, to provide a head cartridge provided with such head, a liquid discharge apparatus, as well as a method for discharging liquid.
It is a further object of the invention to provide a liquid discharge head which comprises a separation member for separating the discharge liquid flow paths communicated with discharge ports for discharging discharge liquid to enable discharge liquid to flow, and the bubbling liquid flow paths to enable bubbling liquid to flow, being provided with the bubble generating areas for creating bubbles used for discharging discharge liquid from the discharge ports, this separation member being provided with the opening portions positioned to face the bubble generating areas, and displacement members provided for the separation member corresponding to the openings, having the free ends to be displaced by bubbles created on the bubble generating areas provided for the separation member, and then, when no bubbles are created on the bubble generating areas, the displacement members interrupt the opening portions, and when bubbles are created on the bubble generating areas, the free ends of the displacement members are displaced to discharge discharge liquid from the discharge ports of this head, and also, to provide a head cartridge provided with such head, a liquid discharge apparatus, as well as a method for discharging liquid.
In accordance with the present invention thus designed, it is possible to prevent such event from taking place as discharge liquid entering around the heat generating members at the time of bubble disappearance and the mixture of discharge liquid and bubbling liquid when the head is left intact for a long time, while maintaining the excellent discharge efficiency by means of the displacement members which are arranged to face the bubble generating areas.